Numerical analysis of methods for aerodynamic loss reduction in axial turbine blades

The objective of this study is to reduce secondary flows causing aerodynamic losses in axial gas turbine blades and to investigate two different methods numerically for reducing losses. These methods are adding fences and slots of different geometries on turbine hub and in turbine case. To this end, solution geometry is formed by using a real blade shape. After that five fences with 2, 3, 5, 7 and 10x1,7 mm (height x wide) size are implemented to solution geometry in turn. After implementing of fences, it is added 3,0x1,7 mm and 1,5x5,2 mm (deepness x wide) casing slots together with each fences and it is analyzed as a combined losses structure. For passage and tip of blades, flows and corresponding vortex structures and pressure distributions are obtained. Evaluating of losses, it is used total pressure loss coefficient at outlet crosssection of passage. In conclusion, the total pressure loss coefficient for baseline case is obtained 1,3746. Other results are obtained as 1,3636, 1,3591, 1,3662, 1,3566, 1,3680 with fences from smaller to large size. Each size of fence provides a loss reduction to some certain extent. Adding 3,0x1,7 mm slot to case geometry with fences, it is obtained 1,3415, 1,3416, 1,3590, 1,3608, 1,3655 of total pressure loss coefficients respectively. And in the case of 5,2x1,7 mm slot, the coefficients are 1,3344, 1,3395, 1,3447, 1,3432, 1,3527. Losses are reduced by fences and both methods applied together. The most reduction is obtained 2,0x1,7mm fence and 5,2x1,7 mm slot. This means 3 % improvement in loss.